RU2620812C2 - Optical bleaching agents for high-quality jet printing - Google Patents

Abstract

FIELD: printing industry.

SUBSTANCE: invention relates to an optical bleaching agent comprising of a mixture of compounds of the formulas

and

wherein R is hydrogen or methyl; Y is an amino acid that is derived from aspartic acid, glutamic acid or iminodiacetic acid and from which the hydrogen atom of the amino group is removed; and M is an alkali metal cation. The invention also relates to an optical bleaching agent comprising a compound of formula (4), to a process for preparing an optical bleaching agent, to a compound of formula (4), to a composition for bleaching paper surface, and to paper optically bleached with an optical bleaching agent.

EFFECT: new optical bleaching agents are obtained, providing a bleaching effect when applied to the paper surface.

14 cl, 1 tbl, 9 ex

Description

FIELD OF THE INVENTION

The present invention relates to new stilbene compounds or mixtures of stilbene compounds, providing an effect of excellent fluorescent whitening when applied to the surface of paper, such as inkjet paper.

State of the art

In recent years, inkjet printing has become a very important means of recording data and images on a sheet of paper. The advantages of this technology are low cost, ease of manufacturing of color images, as well as a relatively high print speed. However, in inkjet printing, high demands are placed on the substrate to ensure fast drying, high density and sharpness of printing, and low color erosion. In addition, the media must have high brightness (gloss). For example, ordinary uncoated paper does not absorb water-based anionic dyes or pigments used for inkjet printing poorly, the ink remains on the surface of the paper for a considerable time, which makes ink diffusion possible and leads to low print definition. One of the ways to reduce the drying time of ink and at the same time ensure high density and clarity of printing is to use special paper coated with silicon dioxide. However, the production of such paper is very expensive.

A partial solution to this problem is described in US Pat. No. 6,207,258, where, to improve the quality of pigmented inkjet printing, it is proposed to treat the carrier with an aqueous sizing solution containing a divalent metal salt. Preferred divalent metal salts are calcium chloride and magnesium chloride. The sizing solution may also contain other standard additives used to process uncoated paper. The list of standard additives includes optical whitening agents, which, as is well known, significantly increase the whiteness of paper and, thus, increase the contrast between the image obtained by inkjet printing and the background. US Pat. No. 6,207,258 does not provide examples of the use of optical whitening agents in conjunction with the invention.

, Horst Behrens, стр. 50, опубл. «Taylor & Francis», 1998).The advantages of using a divalent metal salt, such as calcium chloride, for processing an inkjet carrier can be fully realized only if a compatible water-soluble optical whitening agent is present. However, it is known in the art that at high concentrations of calcium, water-soluble optical whitening agents are more likely to precipitate (see, for example, Tracing Technique in Geohydrology, Werner

Horst Behrens, p. 50, publ. "Taylor &Francis", 1998).

WO 2010/060570 discloses that symmetric diaminostilbene optical whitening agents of formula (1) have unexpectedly good compatibility with sizing compositions containing a divalent metal salt.

The publication WO 2012/013513 claims an improvement over the prior art through the use of specific stilbene whitening agents, the most preferred variants of which (claim 6) have an asymmetric formula (2)

However, there remains a need for a water-soluble optical whitening agent that has improved compatibility with sizing compositions containing a divalent metal salt.

Disclosure of invention

It has been found that optical whitening agents (OAAs) containing a stilbene compound of the formula (4) and / or a mixture of stilbene compounds of the formulas (3), (4) and (5) are surprisingly well compatible with sizing compositions comprising a divalent metal salt , and subsequently provide an improved fluorescent whitening effect when applied to inkjet paper.

Where

R is hydrogen or methyl;

Y is a natural or synthetic amino acid from which the hydrogen atom of the amino group is removed;

M is hydrogen, an alkali metal cation, ammonium, ammonium, mono-, di- or trisubstituted C ₁ -C ₄ linear or branched alkyl radicals; ammonium mono-, di- or trisubstituted with a C ₁ -C ₄ linear or branched hydroxyalkyl radical;

or mixtures of these compounds.

Examples of amino acids from which Y can be derived are alanine, 2-aminobutanoic acid, asparagine, aspartic acid, S-carboxymethylcysteine, cysteic acid, cysteine, glutamic acid, glutamine, glycine, iminodiacetic acid, isoleucine, leucine, methionine, N- methyltaurine, norleucine, norvaline, phenylalanine, 2-phenylglycine, pipecolic acid, proline, methylglycine, serine, taurine, threonine and valine. If the acid has a chiral center, either an optical isomer or a racemic mixture can be used.

In accordance with one aspect of the present invention, Y is a derivative of aspartic, glutamic or iminodiacetic acid.

In accordance with another aspect of the present invention, Y is a derivative of aspartic or iminodiacetic acid, R is methyl, and M is sodium.

A mixture of compounds of formulas (3), (4) and (5) can be prepared, for example, using a multi-stage reaction of cyanogen halide with:

a) an amine of formula (6)

in the form of a free acid, complete or incomplete salt,

(b) a diamine of formula (7)

in the form of a free acid, complete or incomplete salt, and

(c) a mixture of at least one natural or synthetic amino acid, and

(d) diethanolamine and / or diisopropanolamines.

Fluoride, chloride or bromide may be used as cyanurgalide. In one embodiment, cyanuric chloride is used.

Each reaction can be carried out in an aqueous medium, wherein the cyanurhalide is suspended in water or in an aqueous-organic medium, where the cyanurhalide is dissolved in a solvent such as acetone. Each amine can be introduced without dilution or in the form of an aqueous solution or suspension. An arbitrary reaction order of amines is allowed, but it is preferred that aromatic amines be the first to react. Each amine can be reacted in stoichiometric amount or in excess. Typically, aromatic amines are administered in stoichiometric amounts or with a slight excess; the amine mixture used in the last reaction step is usually used in excess of 5-30% in excess of stoichiometry.

To replace the first halogen of cyanurhalide, the reaction is carried out at a temperature in the range of 0-20 ° C and a pH from acidic to neutral, for example, in the range of 2 to 7. To replace the second halogen of cyanurhalide, the reaction is carried out at a temperature in the range of 20-60 ° C The pH is from slightly acidic to slightly alkaline, for example, in the range of 4 to 8. To replace the third halogen of the cyanogen halide, the reaction is carried out at a temperature in the range of 60-102 ° C, i.e. temperature to the boiling point of water under the given reaction conditions, and a pH from slightly acidic to alkaline, for example, in the range from 7 to 10.

The pH value for each of the reactions is generally controlled by the addition of a suitable base, the base being selected based on the desired product composition. Suitable bases are, for example, alkali metals (e.g. lithium, sodium or potassium), hydroxides, carbonates or bicarbonates, or aliphatic tertiary amines, e.g. triethanolamine or triisopropanolamine. If a combination of two or more different bases is used, they can be added in any order or at the same time.

If necessary, adjust the pH with acids; hydrochloric, sulfuric, formic or acetic acid can be used as the acid.

Aqueous solutions containing a mixture of compounds (3), (4) and (5) can optionally be desalted using either membrane filtration or precipitation followed by dissolution with a suitable base. Possible membrane filtration processes are ultrafiltration using polysulfone, polyvinylidene fluoride, cellulose acetate or thin film membranes.

The proportions of compounds (3), (4) and (5) can vary significantly depending on both the composition and the method of administration (sequential or simultaneous) of a mixture of amino acid and dialkanolamine. Each of the compounds (3), (4) and (5) can be represented in the range of 5-80 mol%. In one embodiment, the compound (3) is presented in the range of 5-45 mol%, the compound (4) is presented in the range of 16-65 mol%, and the compound (5) is 5-45 mol%. In another embodiment, the compound (3) is in the range of 15-45 mol%, the compound (4) is 25-60 mol%, and the compound (5) is 5-40 mol%.

Alternatively, the compounds of formulas (3), (4) and (5) can be prepared separately and mixed to produce the optical whitening agent of the invention. Although the compounds of formulas (3) and (5) are known and can be prepared by known methods, the compounds of formula (4) are not known in the art.

Thus, a further aspect of the invention is a compound of formula (4), an optical whitening agent containing said compound of formula (4) and, optionally, additional compounds having whitening properties. Such additional compounds may be selected from compounds of formulas (3) and (5) as described herein, as well as from compounds having whitening properties, but not explicitly disclosed herein.

where R, Y and M were previously defined.

The compound of formula (4) can be manufactured, for example, by:

i) multi-stage reaction

a) a cyanurgalide with an amine of the formula (6)

in the form of a free acid, complete or incomplete salt,

(b) an amine of formula (8)

in the form of a free acid, complete or incomplete salt, and

c) dialkanolamine (diethanolamine or diisopropanolamine),

ii) reduction of the nitro group to an amino group,

iii) a multi-stage reaction with:

a) a reaction product of a cyanurhalide with an amine of the formula (6) and

b) a natural or synthetic amino acid in the form of a free acid, a complete or incomplete salt.

The claimed invention also relates to the use of a compound of formula (4) in compositions for surface whitening of paper.

Another aspect of the present invention is the use for surface bleaching of paper compositions containing a surface sizing agent, an optical whitening agent containing the specified compound of formula (4) or a mixture of compounds (3), (4) and (5), a divalent metal salt and water.

The concentration of the optical whitening agent in the surface whitening composition may be from 0.2 to 30 g / l, for example, from 1 to 15 g / l or from 2 to 12 g / l.

The surface sizing agent is typically an enzymatically or chemically modified starch, for example, oxidized, hydroxyethylated or acetylated starch. Depending on the particular embodiment used, native, anionic, cationic or ampiphatic starch may be selected. The starch source can be any, for example, starch sources can be corn, wheat, potatoes, rice, tapioca and sago.

The concentration of the optical whitening agent in the surface whitening composition may be from 1 to 30% by weight, for example, in the range of 2-20% by weight. or 5-15% of the mass.

Suitable divalent metal salts are selected from the group consisting of calcium chloride, magnesium chloride, calcium bromide, magnesium bromide, calcium sulfate, magnesium sulfate, calcium thiosulfate or magnesium thiosulfate, or a mixture of these components.

In another embodiment, the divalent metal salts are selected from the group consisting of calcium chloride or magnesium chloride, or mixtures of these components.

The concentration of divalent metal salts in the surface whitening composition may be from 1 to 100 g / l, for example, from 2 to 75 g / l or from 5 to 50 g / l.

When using a mixture of calcium salt and magnesium salt as a divalent metal salt, the amount of calcium salt can be from 0.1 to 99.9%.

The pH value of the surface whitening composition is usually from 5 to 13, for example, from 6 to 11.

In addition to a surface sizing agent, an optical whitening agent, a divalent metal salt, and water, the surface whitening composition may also contain both by-products formed during the preparation of the optical whitening agent and other standard paper additives. Examples of such additives are carrier substances, for example polyvinyl alcohol, antifoam additives, wax emulsions, dyes, pigments, monovalent metal salts, for example sodium chloride, dissolution aids, preservatives, complexing agents, cross-linkers, special resins, etc.

In yet another aspect of the invention, an optical whitening agent may be premixed with polyvinyl alcohol to enhance the whitening effect in a surface whitening composition. The level of hydrolysis of polyvinyl alcohol can be any, including values from 60 to 99%.

Optical whitening agents may contain any amount of polyvinyl alcohol, including amounts from 0.1 to 10% of the mass. polyvinyl alcohol.

The surface whitening composition may be applied to the surface of a paper carrier by any of the known surface treatment methods. Application methods include application using a size press, calender, sizing by immersion in a bath, application and spraying of a coating layer. (See, for example, pages 283-286 in Handbook for Pulp & Paper Technologists, GA Smook, 2nd ed., Angus Wilde Publications, 1992 and US Patent Application 2007/0277950.) Preferred method is coating using a size press, such as a pudding press or a dosed press of the composition. A preformed sheet of paper is passed through a twin-shaft pressing device filled with a sizing composition. The paper absorbs a certain amount of the composition, and the remainder of the composition is removed from the roll gap.

The paper carrier comprises a web of cellulosic fibers, which can be synthetic or derived from any fibrous plant, including wood and non-wood fiber sources. Preferably, the cellulosic fibers are obtained from hard and / or soft wood. The fibers may be primary fibers, fibers from regenerated (secondary) cellulose, or a combination of primary and secondary fibers.

The cellulose fibers that make up the paper carrier can be physically and / or chemically modified, for example, as described in chapters 13 and 15, respectively, of the Handbook for Pulp & Paper Technologists, G.A. Smook, ed. 2nd, Angus Wilde Publications, 1992. An example of the chemical modification of cellulose fibers is the addition of optical brightener, as disclosed, for example, in EP 884,312, EP 899,373, WO 02/055646, WO 2006/061399, WO 2007 / 017336, WO 2007/143182, US 2006-0185808 and US 2007-0193707.

The surface whitening composition is made by adding an optical whitening agent and a divalent metal salt to a pre-prepared aqueous solution of a surface sizing agent at a temperature of from 20 to 90 ° C. In one embodiment, the divalent metal salt is added before the optical whitening agent at a temperature of from 50 to 70 ° C.

A paper carrier containing the whitening composition of the invention may be of any ISO brightness, including a brightness of at least 80, at least 90, and at least 95.

A paper carrier containing a whitening composition according to the invention can have any CIE whiteness, including a whiteness of at least 130, at least 146, at least 150 and at least 156. By using the described whitening compositions, it is possible to produce paper with a high degree of whiteness according to CIE, for example 170 or 175 and even higher. When using this whitening composition, a CIE tends to increase the whiteness of the sheet compared to conventional surface whitening compositions containing a similar amount of optical whitening agents.

When applied to a sheet, the whitening composition of the invention has a lower tendency to appear green in comparison with conventional surface whitening compositions containing a similar amount of optical whitening agents. The appearance of a green hue is associated with the saturation of the sheet so that the sheet does not become whiter even with an increase in the number of optical whitening agents. The greening tendency is measured and indicated in the form of a * -b * diagram, where a * and b * are the color coordinates according to the CIE Lab system. Accordingly, the use of the claimed whitening composition allows paper manufacturers to achieve higher CIE whiteness and ISO brightness in the presence of divalent metal salts.

Although the described paper media exhibit improved properties suitable for inkjet printing, these media can also be used for universal and laser printing. For these types of printing, paper cut to size and paper rolls may be required.

The paper carrier of the invention may contain an image that can be obtained using any substance, including dye, pigment or toner.

After forming the image on paper, the print can have any density, for example, at least 1.0, at least 1.2, at least 1.4 and at least 1.6. A description of the methods for measuring optical print density can be found in EP 1775141.

The implementation of the invention

EXAMPLES

The following are examples that more clearly demonstrate the present invention. Unless otherwise indicated, the term "parts" means "mass parts" and "%" means "mass%". "E ¹ ₁ " corresponds to the optical density of a 1% solution, measured at an absorption maximum of about 350 nm in a spectrophotometric cell 1 cm long.

Preparation Example 1

Stage 1: 50.6 parts of aniline-2,5-disulfonic acid are added to 90 parts of water and dissolved with about 30% sodium hydroxide solution at a temperature of about 25 ° C and a pH of about 8-9. The resulting solution is added over about 50 minutes to 36.9 parts of cyanuric chloride dispersed in 54 parts of water, 65 parts of ice and 0.1 parts of a wetting agent. At the same time, the temperature is kept below 5 ° C, using an ice-water bath and adding ice to the reaction mixture if necessary. The pH is maintained at about 4-5 with about 30% sodium hydroxide solution. Mixing is continued at a temperature of about 0 ° -5 ° C until completion of the reaction (3-4 hours).

Step 2: 37.0 parts of 4,4'-diaminostilbeno-2,2'-disulfonic acid are added over approximately 30 minutes. In this case, the pH is maintained at a level of about 8-9 with about 30% sodium hydroxide solution. The resulting mixture is heated to a temperature of about 50-60 ° C until the reaction is complete (2-3 hours).

Stage 3: Then add 15.3 parts of diisopropanolamine and 15.3 parts of L-aspartic acid, gradually raising the temperature to about 100 ° C and maintaining the level of 95-100 ° C until the reaction is complete (4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. Then the temperature is lowered to 25 ° C and the reaction mixture is filtered. The solution was adjusted to a strength sufficient to obtain 920 parts of an aqueous solution with E ¹ ₁ = 61.4, containing 42 parts of a compound of formula (9), 73 parts of a compound of formula (10) and 21 parts of a compound of formula (11).

Compounds (9), (10) and (11) are in a ratio of 31 mol%, 52 mol%. and 14 mol%, respectively.

Preparation Example 2 (Comparative)

Since WO 2012/013513 does not disclose a method for preparing the 3 - [(2-hydroxylpropyl) amino] propionitrile necessary to prepare the preferred embodiment of claim 6, the method disclosed in Example 1 of GB 1313469 is followed.

Preparation 1 is followed until stage 2 is completed. Then 3 - [(2-hydroxylpropyl) amino] propionitrile prepared from 8.6 parts of isopropanolamine, 6.1 parts of acrylonitrile and 15.3 parts of diisopropanolamine is added. The temperature is gradually raised to about 95 ° C and maintained at 95-98 ° C until completion of the reaction (about 4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. After lowering the temperature to 50 ° C, and the reacted mixture is filtered. The solution was adjusted to a strength sufficient to obtain 920 parts of an aqueous solution with E ¹ ₁ = 61.4, containing 31 parts of a compound of formula (9), 38 parts of a compound of formula (12), 23 parts of a compound of formula (13), 14 parts of a compound of formula (14), 15 parts of a compound of formula (15) and 4 parts of a compound of formula (16).

Compounds (9), (12), (13), (14), (15) and (16) are in the ratio of 24 mol%, 31 mol%, 18 mol%, 11 mol%, 12 mol% . and 3 mol%, respectively.

Preparation Example 3

Preparation 1 is followed until stage 2 is completed. Then 12.2 parts of diisopropanolamine and 18.4 parts of L-aspartic acid are added, the temperature is gradually raised to about 100 ° C and maintained at 95-100 ° C until the reaction will end (about 4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. Then the temperature is lowered to 25 ° C, and the reaction mixture is filtered. The solution was adjusted to a strength sufficient to obtain 722 parts of an aqueous solution with E ¹ ₁ = 76.6, containing 29 parts of a compound of formula (9), 69 parts of a compound of formula (10) and 39 parts of a compound of formula (11). Compounds (9), (10) and (11) are in a proportion of 22 mol%, 51 mol%. and 27 mol%, respectively.

Preparation Example 4

Preparation 1 is followed until stage 2 is completed. Then 9.2 parts of diisopropanolamine and 21.4 parts of L-aspartic acid are added, the temperature is gradually raised to about 100 ° C and maintained at 95-100 ° C until the reaction will end (about 4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. After that, the temperature is lowered to 25 ° C, and the reaction mixture is filtered. The solution was adjusted to a strength sufficient to obtain 665 parts of an aqueous solution with E ¹ ₁ = 84.7 containing 17 parts of a compound of formula (9), 66 parts of a compound of formula (10) and 57 parts of a compound of formula (11). Compounds (9), (10) and (11) are in a proportion of 12 mol%, 48 mol%. and 40 mol%, respectively.

Preparation Example 5

Preparation 1 is followed until Stage 2 is completed. Then 18.4 parts of diisopropanolamine and 12.2 parts of L-aspartic acid are added, the temperature is gradually raised to about 100 ° C and maintained at 95-100 ° C until the reaction will end (about 4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. Then the temperature was lowered to 25 ° C, and the reaction mixture was filtered. The solution was adjusted to a strength sufficient to obtain 575 parts of an aqueous solution with E ¹ ₁ = 86.5, containing 52 parts of a compound of formula (9), 54 parts of a compound of formula (10) and 17 parts of a compound of formula (11). Compounds (9), (10) and (11) are in a proportion of 43 mol%, 43 mol%. and 13 mol%, respectively.

Preparation Example 6

Preparation 1 is followed until stage 2 is completed. Then 21.4 parts of diisopropanolamine and 9.2 parts of L-aspartic acid are added, the temperature is gradually raised to about 100 ° C and maintained at 95-100 ° C until the reaction will end (about 4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. Then the temperature was lowered to 25 ° C, and the reaction mixture was filtered. The solution was adjusted to a strength sufficient to obtain 615 parts of an aqueous solution with E ¹ ₁ = 85.9, containing 77 parts of a compound of formula (9), 47 parts of a compound of formula (10) and 56 parts of a compound of formula (11). Compounds (9), (10) and (11) are in a proportion of 43 mol%, 26 mol%. and 30 mol%, respectively.

Preparation Example 7

Follow Preparation Example 1 to complete Step 2. Then, 15.3 parts of diisopropanolamine and 15.3 parts of sodium iminodiacetate are added, the temperature is gradually raised to about 100 ° C and maintained at 95-100 ° C until the reaction is complete (about 4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. Then the temperature was lowered to 25 ° C, and the reaction mixture was filtered. The solution was adjusted to a strength sufficient to obtain 608 parts of an aqueous solution with E ¹ ₁ = 82.1, containing 29 parts of a compound of formula (9), 46 parts of a compound of formula (17) and 51 parts of a compound of formula (18).

Compounds (9), (17) and (18) are in a proportion of 24 mol%, 37 mol%. and 39 mol%, respectively.

Preparation Example 8

Preparation 1 is followed until stage 2 is completed. 15.3 parts of diisopropanolamine and 15.3 parts of L-aspartic acid are then added, the temperature is gradually raised to a temperature of about 100 ° C and maintained at 95-100 ° C until the reaction will not end (about 4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. Then the temperature was lowered to 25 ° C, and the reaction mixture was filtered. The solution was adjusted to a strength sufficient to obtain 586 parts of an aqueous solution with E ¹ ₁ = 84.5 containing 35 parts of a compound of formula (11), 56 parts of a compound of formula (19) and 33 parts of a compound of formula (20).

Compounds (11), (19) and (20) are in a proportion of 27 mol%, 45 mol%. and 28 mol%, respectively.

Preparation Example 9

Preparation 1 is followed until stage 2 is completed. 15.3 parts of diisopropanolamine and 16.9 parts of L-glutamic acid are then added, the temperature is gradually raised to about 100 ° C and maintained at 95-100 ° C until the reaction will end (about 4 hours), keeping the pH at about 8-9 with about 30% sodium hydroxide solution. Then the temperature was lowered to 25 ° C, and the reaction mixture was filtered. The solution was adjusted to a strength sufficient to obtain 599 parts of an aqueous solution with E ¹ ₁ = 87.4, containing 28 parts of a compound of formula (9), 67 parts of a compound of formula (21) and 38 parts of a compound of formula (22).

Compounds (9), (21) and (22) are in a proportion of 22 mol%, 50 mol%. and 27 mol%, respectively.

Surface application example.

Surface whitening compositions are prepared by adding aqueous solutions obtained according to examples 1 and 2 in a concentration range from 0 to 40 g / l (0 to about 8.0 g / l of optical brightener), to a stirred aqueous solution of calcium chloride (35 g / l ) and anionic starch (50 g / l) (Penford Starch 260) at 60 ° C. The sizing solution is allowed to cool, then it is poured between the moving rollers of the laboratory size press and applied to a commercial, glued AKD (alkyl ketene dimer), 75 g / m bleached paper base sheet. The treated paper is dried for 5 minutes at 70 ° C in a flat-surface dryer.

The dried paper was brought to ambient conditions and then CIE whiteness was measured using a calibrated Auto Elrepho spectrophotometer. The measurement results are shown in table 1.

The results shown in table 1, clearly demonstrate that the use of the claimed compositions allows to achieve greater whiteness and, in addition, to achieve improved characteristics of red (a higher indicator a *) and blue (a larger value after the minus sign in b *) shades.

Claims (39)

1. Optical whitening agent containing a mixture of compounds of formulas (3), (4) and (5)

Where R is hydrogen or methyl; Y is the sodium salt of an amino acid that is a derivative of aspartic acid, glutamic acid or iminodiacetic acid and from which the hydrogen atom of the amino group is removed, and M is an alkali metal cation. 2. The agent according to claim 1, in which Y is a derivative of aspartic acid or iminodiacetic acid, R represents methyl, and M represents sodium. 3. Optical whitening agent containing a compound of formula (4)

Where R is hydrogen or methyl; Y is the sodium salt of an amino acid that is a derivative of aspartic acid, glutamic acid or iminodiacetic acid and from which the hydrogen atom of the amino group is removed, and M is an alkali metal cation. 4. The agent according to claim 3, in which Y is a derivative of aspartic acid or iminodiacetic acid, R is methyl, and M is sodium. 5. A method of obtaining an optical whitening agent containing compounds of formulas (3), (4) and (5) according to any one of paragraphs. 1-4, in which carry out a multi-stage reaction of cyanogen halide with: a) an amine of the formula (6)

in the form of a free acid, complete or incomplete salt, (b) a diamine of formula (7)

in the form of a free acid, complete or incomplete salt, and c) a mixture of at least one amino acid which is a derivative of aspartic acid, glutamic acid or iminodiacetic acid, and d) diethanolamine and / or diisopropanolamine. 6. The method according to p. 5, in which the substitution of the first halogen of cyanurhalide is carried out at a temperature in the range from 0 to 20 ° C under pH from acidic to neutral, and the substitution of the second halogen of cyanurhalide is carried out at a temperature in the range of from 20 to 60 ° C conditions from weakly acidic to slightly alkaline at a pH of from 4 to 8, and the substitution of the third halogen cyanogen halide is carried out at a temperature in the range from 60 to 102 ° C. from slightly acidic to alkaline at a pH of from 7 to 10. 7. The method according to p. 5 or 6, in which the compound (3) is used in the concentration range of 5-45 mol%, the compound (4) in the range of 15-65 mol%, and the compound (5) in the range of 5 -45 mol%. 8. The compound of formula (4)

Where R is hydrogen or methyl; Y is the sodium salt of an amino acid that is a derivative of aspartic acid, glutamic acid or iminodiacetic acid, from which the hydrogen atom of the amino group is removed, M is an alkali metal cation. 9. The composition for whitening the surface of the paper containing a surface sizing agent, an optical whitening agent according to any one of paragraphs. 1-4, a divalent metal salt and water. 10. The composition according to p. 9, in which the concentration of the optical whitening agent is from 0.2 to 30 g / L. 11. The composition according to p. 10, which further comprises polyvinyl alcohol. 12. The composition according to p. 11, which further comprises polyvinyl alcohol. 13. The composition according to any one of paragraphs. 9-12, intended for use in a size press, sizing calender, glue bath, device for applying and / or spraying a coating. 14. Paper optically bleached using an optical whitening agent according to any one of claims. 1-4.